Data transceivers of the type used for remote access to vehicles require reliability, small size and low power consumption. A remote access system comprises a base unit in a vehicle and a remote unit to be carried by the operator. The base and remote units are coupled by a UHF radio link for a bi-directional exchange of data when activated to verify that the remote unit is authorized to command vehicle access. It is desired that the remote unit be small enough to be carried on a key chain and have a battery sufficient for several years operation. Accordingly a simple, low power consumption transceiver circuit is desired. It is further desired that the unit have high temperature stability.
The U.S. Pat. No. 4,749,964 to Ash entitled "Super-regenerative Detector Having a SAW device in the Feedback Circuit", which is incorporated herein by reference, discloses a receiver having a simple circuit and including a surface acoustic wave (SAW) device in the feedback circuit of the RF oscillator. The detector includes a quenching oscillator coupled to the RF oscillator to turn the RF oscillator on and off at a given frequency and duty cycle, and an input RF signal is superimposed on the RF oscillator to modulate the oscillation by increasing the duty cycle. The modulation is recovered by low pass filtering the output of the oscillator. The same device is further described in the RF Monolithics applications note by Ash, "A Low Cost Superregenerative SAW Stabilized Receiver".